In recent years, there are many portable phones equipped with GPS function. The GPS function allows the portable phones to acquire positional information.
When the GPS function of conventional portable phone is used, map information needs to be updated via a network (communication network) as the positional information that changes every moment. Therefore, a CPU of the portable phone periodically acquires the positional information from a GPS module.
Incidentally, in the portable phone, when the GPS function is used, the CPU needs to periodically access the GPS module to acquire the positional information that changes every moment. As a result, the operational rate of the CPU increases, leading to an increase in power consumption of the portable phone.
However, for example, the time intervals at which the CPU updates the map information are different between the low traveling speed such as walking transfer and the fast traveling speed such as a vehicle transfer. Acquiring the positional information at the same time intervals even when the traveling speed is low, may lead to a waste of power consumption.
Patent Literatures 1 to 3 describe conventional arts the objective of which is to reduce power consumption of a portable terminal device which is equipped with a location means to locate the current position.
Paragraph 40 of Patent Literature 1 describes a portable terminal device that locates the current position at predetermined intervals in a GPS method. Moreover, paragraph 49 of Patent Literature 1 explains that based on the traveling speed obtained as a result of GPS location, a determination is made as to whether a person is aboard a vehicle or not (walking or the like). Moreover, paragraph 55 of Patent Literature 1 explains that the GPS location comes to a halt when a person is aboard a vehicle.
Paragraph 31 of Patent Literature 2 describes a technique for stopping the location operation of the current position when the amount of remaining battery charge of a portable phone is less than or equal to a predetermined value.
Patent Literature 3 describes a positional information location system that includes a specifying means, which specifies a position that is a predetermined distance away from the current position of a terminal on a map and that is on a predetermined route along which the terminal travels as a position to be located next time; and a management means, which calculates the traveling time required for the terminal to move from the current position to the position to be located next time and stops the position location operation of the terminal during the traveling time.